1. Field of the Invention
The present invention relates to a method of manufacturing a molding and, more particularly, to a method of manufacturing a molding in which a filler or an additive is concentrated on an arbitrary portion or distributed at a gradient concentration to improve the properties of the molding or to impart a new function to the molding.
2. Description of the Related Art
It has been known that the physical properties such as mechanical strength, heat resistance, and electrical characteristics of the molding can be improved by mixing various fillers in a resin. In this technique, by changing the types, amounts, and the like of the fillers properly in accordance with its applications, the properties of the obtained molding can be controlled.
According to a recent attempt, the physical properties of the molding also can be improved or a new function can be imparted by changing the concentration of a filler gradiently in the molding. However, a proper method of so changing the concentration of the filler in the molding has not been found.
In addition, in the conventional resin compositions, various additives such as a mold release agent, a flame retardant, an adhesion imparting agent, and an antistatic agent are uniformly dispersed into the resins. In this case, the additives, for example, the mold release agent cannot perform a mold release effect if the mold release agent is not precipitated on the surface of the molding. However, an effective method to precipitate the mold release agent has not been found. For this reason, an excessive mold release agent addition into the resin composition is unavoidable. However, the mold release agent not only improves the mold release characteristics of the molding but also reduces adhesion properties, therefore the excessive mold release agent is not preferably added. Such a problem is posed by not only the mold release agent but also the flame retardant, the adhesive imparting agent, and the antistatic agent. Therefore, a molding method capable of precipitating an arbitrary additive at an arbitrary portion such as an interface between a molding and a mold or an insert without excessively adding the additive has been strongly demanded.